Page History

Page info

infoType	Modified date
prefix	Last modified on
type	Flat

A few times per year, the analysed low level winds, eg the 10m winds, become very unrealistically large in a particular location, which varies amongst a few apparently preferred locations. The largest values seen so far are about 300 ms^-1.

The tables below give details when the components of the 10m winds, the 10 metre U wind component and 10 metre V wind component, exceed 50 ms^-1. This value is an arbitrary one which may capture real wind events, such as hurricanes and typhoons.

This problem occurs towards the end of the data assimilation windows (9-21 UTC and 21-9 UTC) because of an instability in the analysis method.

From 19 February 2020 onwards, the ERA5 system has examined the 10m wind components and if the magnitude of either component exceeds 50 ms^-1, then the analysed parameters are replaced with the "4v" parameters. These latter parameters are similar to the analysed ones, but don't usually suffer from such large values. For more information on 4v and data assimilation, see "Part II Data Assimilation" of the IFS documentation (CY41R2 for ERA5).

The choice of a 50 ms^-1 cut off is an arbitrary one, which could miss spurious values that are less than 50 ms^-1. This may well occur in the one or two hours just before the critical value of 50 ms^-1 is reached. It is also possible that this cut off point could penalise realistic winds, such as in hurricanes. However, given the spatial resolution of ERA5 data (with a grid spacing of 31km), it is thought that in general, 10m wind components higher than 50 ms^-1 are not realistic in ERA5, even if the observed magnitude is higher. This is illustrated in Fig. 1 for Hurricane Ivan in the Caribbean on 12 September 2004 at 20 UTC, where the analysed winds are compared with the 4v winds. The minimum value of the analysed 10 metre V wind components is -53 ms^-1 (see Event 57, Table 2), while the minimum value of the 4v 10 metre V wind components is -29 ms^-1. Even though the analysed wind speeds are not as large as the observed ones (the estimated peak wind speeds for Ivan were of order 70 ms^-1), the 4v winds are thought to give a more realistic representation of the winds, for this resolution.

Fig. 1a	Fig. 1b
Image Added	Image Added
Fig. 1a. The analysed 10m winds for 12 September 2004, 20 UTC, featuring Hurricane Ivan. The regional plot domain shows the Caribbean and Gulf of Mexico.	Fig. 1b. As Fig 1a, but for the 4v 10m winds.

For dates before this system check was introduced into ERA5 (i.e. for the period January 1979 to 18 February 2020), the two tables below give details when the analysed 10m wind components (the 10 metre U wind component and 10 metre V wind component) exceed 50 ms^-1. The CDS API script below can be used to retrieve the "4v" 10m wind components, which don't usually suffer from this large wind problem.

Expand

title	CDS API script to retrieve the "4v" 10m winds

Code Block

#!/usr/bin/env python
import cdsapi
 
c = cdsapi.Client()
c.retrieve('reanalysis-era5-complete', {     # do not change this!
    'stream'  : 'oper',
    'type'    : '4v',
    'levtype' : 'sfc',
    'param'   : '165.128/166.128',
    'date'    : '1986-07-23',
    'time'    : '21',
    'step'    : '12',
    'grid'    : '0.25/0.25', # Latitude/longitude grid: east-west (longitude) and north-south resolution (latitude). Default: reduced Gaussian grid
    'format'  : 'grib', # Default: grib, supported netcdf.
}, 'outfile.grib')

This CDS API script can be used to retrieve the "4v" 10m wind components from the ECMWF data archive, MARS. For more information on how to use CDS API scripts, see How to download ERA5. For the temporal specification, the CDS uses the validity date and time, whereas MARS uses date, time and step (there is further discussion of step in the section "Date and time specification" of the ERA5 data documentation). The 4v model trajectories begin from 9 and 21 UTC and you should use the hourly steps from 1 to 12 hours. In this example in the script above, the validity date/time would be given by adding the step, 12 hours, to the time, 21 UTC, thereby yielding a validity date/time of 1986-07-24 at 9 UTC, which is the 12th event in Table 1 below, for the 10m U.

2100

Event	Date	Time	Latitude	Longitude	10m U
1	19790417	900	-74.051	164.160	7.2323150635e+01
2	19800330	700	-1.827	280.406	-5.9812698364e+01
3	19800330	800	-1.827	280.406	-9.8439865112e+01
4	19800330	900	-1.827	280.406	-7.1381820679e+01
5	19820908	700	-74.051	164.160	-6.9596405029e+01
6	19820908	800	-74.051	164.160	-5.2189117432e+01
7	19821024	2100	-74.051	164.160	-1.5377770996e+02
8	19841004	700	-74.051	164.160	-5.5174591064e+01
9	19841004	800	-74.051	164.160	-6.8660507202e+01
10	19841004	900	-74.051	165.120	-7.1647964478e+01
11	19860724	800	-74.051	164.160	-8.8280364990e+01
12	19860724	900	-74.051	164.160	-2.9203100586e+02
13	19871016	2000	-74.051	164.160	-9.4200180054e+01
14	19871016	2100	-74.051	164.160	-1.5219485474e+02
15	19890711	2100	38.080	78.333	7.0804840088e+01
16	19890912	800	-74.051	164.160	-8.3815658569e+01
17	19890912	900	-74.051	164.160	-1.6730293274e+02
18	19900402	700	-74.051	164.160	5.8469223022e+01
19	19930624	600	-74.051	164.160	6.0172592163e+01
20	19930624	700	-74.051	164.160	1.0357415771e+02
21	19930624	800	-74.051	164.160	7.8659744263e+01
22	19930624	900	-74.051	164.160	5.5145812988e+01
23	19930705	2000	38.080	78.333	8.0320663452e+01
24	19930705	2100	38.361	78.398	5.9963912964e+01
25	19940914	2100	-74.051	164.160	-7.9331817627e+01
26	19970607	700	-74.051	164.160	5.8002792358e+01
27	19970607	800
Date	Time	Latitude	Longitude	10m U
19790417	900	-74.051	164.160	7.2323150635e+01
19800330	700	-1.827	280.406	-5.9812698364e+01
19800330	800	-1.827	280.406	-9.8439865112e+01
19800330	900	-1.827	280.406	-7.1381820679e+01
19820908	700	-74.051	164.160	-6.9596405029e+01
19820908	800	-74.051	164.160	-5.2189117432e+01
19821024	2100	-74.051	164.160	-1.5377770996e+02
19841004	700	-74.051	164.160	-5.5174591064e+01
19841004	800	-74.051	164.160	-6.8660507202e+01
19841004	900	-74.051	165.120	-7.1647964478e+01
19860724	800	-74.051	164.160	-8.8280364990e+01
19860724	900	-74.051	164.160	-2.9203100586e+02
19871016	2000	-74.051	164.160	-9.4200180054e+01
19871016	2100	-74.051	164.160	-1.5219485474e+02
19890711	2100	38.080	78.333	7.0804840088e+01
19890912	800	-74.051	164.160	-8.3815658569e+01
19890912	900	-74.051	164.160	1.0099096680e+02
28	19970923	1900	-74.051	164.160	1.6730293274e3710269165e+02
29	1990040220010423	7002100	-74.051	164.160	5-8.8469223022e0685379028e+01
30	1993062420040327	600800	-74.051	164.160	-6.0172592163e4567825317e+01
31	1993062420050314	700800	-741.051827	164280.160406	1-6.0357415771e1867416382e+0201
32	1993062420050314	800900	-741.051827	164280.160406	7-9.8659744263e2169509888e+01
33	2006030419930624	900	-741.051827	164280.160125	5-6.5145812988e3722732544e+01
34	1993070520060328	2000800	38-1.080827	78280.333406	8-5.0320663452e7734420776e+01
35	1993070520060328	2100900	38-1.361827	78280.398406	5-1.9963912964e1018218994e+0102
36	1994091420070331	2100	-74.051	164.160	-78.9331817627e7419113159e+01
37	1997060720090303	700	-741.051827	164280.160406	5-8.8002792358e9056137085e+01
38	1997060720090303	800	-741.051827	164280.160406	-1.0099096680e3375457764e+02
39	1997092320090303	1900900	-741.051827	164280.160406	1-2.3710269165e0406346130e+02
40	2001042320091218	2100	-7443.051138	16475.160000	-85.0685379028e9425277710e+01
41	2004032720100325	800900	-741.051827	164280.160688	-65.4567825317e4004959106e+01
42	2005031420110127	800900	-1.827	280.406	-65.1867416382e3115798950e+01
43	2005031420111224	9002100	-143.827138	28075.406000	-96.2169509888e8307769775e+01
44	2013071920060304	9002100	-174.827051	280164.125160	-6.3722732544e1746520996e+01
45	2006032820140426	800700	-1.827265	280.406688	-5.7734420776e7151275635e+01
46	2006032820140426	900700	-1.827546	280.406	-1.1018218994e+02	20070331	-74.051	164.160	8.7419113159e5247161865e+01
47	2009030320140426	700800	-1.827265	280.406688	-87.9056137085e2114089966e+01
48	2009030320140426	800	-1.827546	280.406	-1.3375457764e4157341003e+02
49	2009030320140426	900	-1.827546	280.406	-2.0406346130e0927426147e+02
50	2009121820160522	21002000	43-74.138051	75164.000160	-56.9425277710e6684082031e+01
51	2010032520160522	9002100	-174.827051	280164.688160	-5.4004959106e9349365234e+01
52	2016092920110127	9002100	-174.827051	280164.406160	-56.3115798950e5295028687e+01
53	2011122420161128	2100	4342.138857	75.000375	-65.8307769775e2441085815e+01
20130719	2100	-74.051	164.160	-6.1746520996e+01
20140426	700	-1.265	280.688	5.7151275635e+01

Table 1: Occurrences when the 10 metre U wind component exceeds 50 ms^-1.

Event	Date	Time	Latitude	Longitude	10m V
1	19790401	2100	-5.480	137.812	-9.6993362427e+01
2	19800330	900	-1.827	20140426	700	-1.546	280.406	-85.5247161865e0487777710e+01
3	2014042619800831	8001900	-15.265199	280137.688531	7-6.2114089966e5852249146e+01
4	1980083120140426	8002000	-15.546199	280137.406531	-15.4157341003e0360015869e+0201
5	2014042619821024	9002100	-174.546051	280164.406160	-25.0927426147e4236557007e+0201
6	2016052219830930	2000	-7442.051576	16484.160815	-65.6684082031e0510147095e+01
7	2016052219830930	2100	-7442.051576	16484.160815	-56.9349365234e1684814453e+01
8	2016092919840811	21001800	-745.051480	164137.160812	61.5295028687e3961134338e+0102
9	2016112819840811	21001900	42-5.857199	75137.375531	-51.2441085815e2407348633e+01

Table 1: Occurrences when the 10 metre U wind component exceeds 50 ms^-1.

190086714050293e48081285311660767e0148081288643951416e

Date	Time	Latitude	Longitude	10m V
02
10	19840811	2000	-5.199	137.531	1.3110269165e+02
11	19840811
19790401	2100	-5.480199	137.812531	-91.6993362427e2531871033e+0102
12	1980033019850812	9001900	-15.827199	280137.406531	-56.0487777710e5993698120e+01
13	1985081219800831	19002000	-5.199480	137.531812	-68.5852249146e7721923828e+01
14	1980083119850812	20002100	-5.199480	137.531812	-51.0360015869e1631915283e+0102
15	1982102419851116	2100	-745.051480	164137.160812	5-8.4236557007e0120529175e+01
16	1983093019860724	2000900	42-74.576051	84164.815160	51.0510147095e3616104126e+0102
17	1983093019871016	2100	42-74.576051	84164.815160	6.1684814453e7936035156e+01
18	1984081119890420	18002000	-5.480	137.812	1.3961134338e+02	19840811		-5.1995810119629e+01
19	19890420	2100	137.531	1.2407348633e+02	19840811	2000	-5.199480	137.531812	-1.3110269165e2454008484e+02
20	1984081119890711	2100	-538.199361	13778.531398	1.2531871033e4824528503e+02
21	1985081219890912	1900900	-574.199051	137164.531160	6.5993698120e3201354980e+01
22	1985081219901117	2000600	-541.480171	13739.812960	8-7.7721923828e1991546631e+01
23	1985081219901117	2100700	-541.480171	13739.812600	1-7.1631915283e2909973145e+0201
24	1985111619910620	21002000	-5.480	137.812	-89.0120529175e5385955811e+01
25	1986072419910620	9002100	-745.051761	164138.160094	1.3616104126e6087461853e+02
1987101626	2100	-74.051	164.160	6.7936035156e+01
19890420	2000	-5.480	137.812	-5.5810119629e+01
19920415	800	20.094	84.375	5.1177642822e+01
27	1992110819890420	2100	-5.480199	137.812531	-15.2454008484e9594894409e+0201
1989071128	210019921113	38.361	78.398	1.4824528503e+02
19890912	900	-74.051	164.160	6.3201354980e+01
19901117	600	41.171	39.960	-7.1991546631e+01
19901117	700	41.171	39.600	-7.2909973145e+01
1800	-5.480	137.812	-7.4539321899e+01
29	19921113	1900	-5.761	137.812	-1.4339295959e+02
30	19921113	2000	-5.480	137.531	-1.5561082458e+02
31	19921113	2100	19910620	2000	-5.480	137.812531	9-1.5385955811e7285772705e+0102
32	1991062019921123	2100	-543.761138	13874.094625	1-7.6087461853e4817504883e+0201
33	1992041519930705	8002000	2038.094361	8478.375398	51.1177642822e7013420105e+0102
34	1992110819930705	2100	-538.199361	13778.531398	-56.9594894409e0669006348e+01
35	1992111319930815	18002000	-531.480335	13772.812000	-71.4539321899e2063990784e+0102
36	1992111319950127	19002100	-540.761890	13739.812600	-19.4339295959e3620895386e+0201
37	1992111319960710	2000	-5.480	137.531812	-17.5561082458e3640014648e+0201
38	1992111319960710	2100	-5.480	137.531812	-1.7285772705e1385275269e+02
39	1992112319970422	2100	4340.138890	7439.625240	-71.4817504883e3644331360e+0102
40	1993070519970617	20001700	3839.361766	7889.398297	-1.7013420105e0041018677e+02
41	1997062619930705	21001900	38-5.361480	78137.398812	65.0669006348e7410095215e+01
42	1993081519970626	2000	31-5.335480	72137.000812	-1.2063990784e2612721252e+02
43	1997062619950127	2100	40-5.890480	39137.600812	-98.3620895386e5113784790e+01
44	1997081719960710	2000	-5.480	137.812	75.3640014648e6425781250e+01
45	1997081719960710	2100	-5.480	137.812	1.1385275269e4044223022e+02
46	1997042219970923	21001900	40-74.890051	39164.240160	-15.3644331360e1563308716e+0201
47	1997061720010127	1700600	3941.766171	8939.297960	-1.0041018677e2166479492e+02
48	1997062620010127	1900700	-541.480171	13739.812960	58.7410095215e3281478882e+01
49	2002060219970626	20002100	-538.480923	13783.812320	1-6.2612721252e7981185913e+0201
50	1997062620030516	2100	-5.480	137.812	86.5113784790e4198028564e+01
51	2003070419970817	2000	-540.480328	13784.812240	5.6425781250e8809799194e+01
52	1997081720040711	21001800	-540.480328	13787.812480	1.4044223022e6328262329e+02
53	2004071119970923	1900	-7440.051328	16487.160480	-57.1563308716e7149871826e+01
20010127	600	41.171	39.960	1.2166479492e+02
20010127	700	41.171	39.960	8.3281478882e+01
20020602	2100	38.923	83.320	-6.7981185913e+01
54	20040803	2100	-5.199	137.531	-5.1051910400e+01
55	20040830	2000	-5.199	137.531	-7.2028549194e+01
56	2004083020030516	2100	-5.480199	137.812250	6-1.4198028564e5628892517e+0102
57	2003070420040912	2000	4019.328532	84277.240031	-5.8809799194e3294830322e+01
58	2004071120050805	18002000	40-5.32848087	137.480812	1-9.6328262329e3390945435e+0201
59	2004071120050805	19002100	40-5.32848087	137.480812	7-9.7149871826e8295639038e+01
60	2004080320051208	2100800	-540.199890	13739.531960	-56.1051910400e6637542725e+01
61	2004083020060304	2000900	-51.199546	137280.531406	-7.2028549194e0116149902e+01
62	2004083020060612	21001900	-5.199480	137.250812	-16.5628892517e8560852051e+0201
63	2004091220060612	2000	19-5.532480	277137.031812	-51.3294830322e0062788391e+0102
64	2005080520060612	20002100	-5.480	137.812	-9.3390945435e+01
20050805	2100	-5.480	137.812	-9.8295639038e+01
	1.1736833191e+02
65	20061210	700	41.171	39.600	5.8087677002e+01
66	20061210	800	41.171	39.600	5.1876373291e+01
67	20061219	700	41.171	20051208	800	40.890	39.960	6.6637542725e5212203979e+01
68	2006030420061219	900800	-141.546171	28039.406600	-75.0116149902e0869308472e+01
69	2007122720060612	1900600	-541.480171	13739.812600	67.8560852051e9303802490e+01
70	2006061220071227	2000700	-541.480171	13739.812960	1.0062788391e0291072083e+02
71	2006061220071227	2100800	-541.480171	13739.812960	18.1736833191e6426681519e+0201
72	2006121020090303	700900	41-1.171827	39280.600406	5-6.8087677002e8449584961e+01
73	2006121020091218	8002000	4143.171138	3974.600625	5-6.1876373291e3902404785e+01
74	2006121920091218	7002100	4143.171138	3974.960625	6-1.5212203979e5077589417e+0102
75	2006121920100110	8002100	4140.171890	39.600960	-5.0869308472e4371688843e+01
76	2011120720071227	6002100	41.171	39.600960	7-5.9303802490e2954406738e+01
77	2007122720111224	7002000	4143.171138	3974.960625	1-8.0291072083e1969665527e+0201
78	2007122720111224	8002100	4143.171138	3974.960625	8-1.6426681519e0727139282e+0102
79	2009030320120629	9002000	-15.827480	280137.406812	-6.8449584961e8156173706e+01
80	2009121820120629	20002100	43-5.138480	74137.625812	-65.3902404785e3109390259e+01
81	2009121820130727	21001900	4338.138080	7478.625333	-16.5077589417e0674041748e+0201
82	2010011020131224	2100600	4041.890171	39.960	-56.4371688843e8190124512e+01
83	2013122420111207	2100700	41.171	39.960600	-56.2954406738e7012496948e+01
84	2011122420131224	2000800	4341.138171	7439.625600	-85.1969665527e1414718628e+01
85	2014042620111224	2100700	43-1.138265	74280.625406	-15.0727139282e4881195068e+0201
86	2012062920140426	2000700	-52.480108	137280.812688	6-5.8156173706e8466461182e+01
87	2012062920140426	2100800	-51.480546	137280.812688	5-8.3109390259e5272201538e+01
88	2013072720140426	1900900	38-1.080546	78280.333688	6-1.0674041748e0531086731e+0102
89	2013122420150912	6001900	41-5.171199	39137.960531	6.8190124512e4281372070e+01
90	2013122420160516	7001900	41-5.171480	39137.600812	61.7012496948e1651092529e+0102
91	2013122420160516	8002000	41-5.171480	39137.600531	51.1414718628e5173913574e+0102
92	2014042620160516	7002100	-15.265480	280137.406812	57.4881195068e3943984985e+01
93	2014042620160531	7002000	-25.108480	280137.688812	-58.8466461182e6714050293e+01
94	2014042620160531	8002100	-15.546480	280137.688812	-8.5272201538e5311660767e+01
95	2014042620160825	9001900	-15.546480	280137.688812	-18.0531086731e8643951416e+0201
96	2015091220160825	19002000	-5.199	137.531	6.4281372070e8540237427e+01
20160516	1900	-5.480	137.812	1.1651092529e+02

97	20161128	2000	43.138	74.625	-8.1585525513e+01
98	20161128	2100	43.138	74.625	-1.6854412842e+02
99	20171011	2100	20160516	2000	-5.480	137.531812	1.5173913574e1839462280e+02
100	2016051620180914	2100	-5.480	137.812	75.3943984985e5520050049e+01
101	2019111620160531	20001800	-5.480	137.812	7.	6125183105e+01
102	2016053120191116	21001900	-5.	199	137.	531	1.	4759844971e+	02
103	2016082520191116	19002000	-5.	199	137.	531	7.	8542388916e+01
20160825	2000	-5.199	137.531	6.8540237427e+01
20161128	2000	43.138	74.625	-8.1585525513e+01
20161128	2100	43.138	74.625	-1.6854412842e+02
20171011	2100	-5.480	137.812	1.1839462280e+02
20180914	2100	-5.480	137.812	5.5520050049e+01

...

Table 2: Occurrences when the 10 metre V wind component exceeds 50 ms^-1.

Info

icon	false

_{This document has been produced in the context of the Copernicus Climate Change Service (C3S).}

_{The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.}

_{The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.}

Space shortcuts

Page tree

Versions Compared

Old Version 14

New Version Current

Key

Related articles